Lecture 7: Anatomy and Physiology of Normal Swallowing

Question 1

What are the major events in each phase of swallowing? Which muscles and cranial nerves are involved?

Answer 1

1. Oral
   
   • Oral Preparatory = make a bolus that is ready for swallow
     
     • Form bolus, mix with saliva
   • Oral Transport = move the bolus from oral cavity to pharynx
     
     • Move bolus into oropharynx
2. Pharyngeal = from pharynx through esophagus
   
   • VP port closes - prevents nasal regurgitation
   • Pharynx shortens and expands, contracting behind the bolus
   • Airway closes
   • Larynx elevates
   • Upper esophageal segment (UES)/ pharyngoesophageal segment (PES) relaxes and opens
3. Esophageal = from esophagus to stomach

Question 2

What and where are the lateral and anterior sulci, the pyriform sinuses, and the valleculae?

Answer 2

Anterior sulci

• Between the mandible or maxilla and the lips

Pyriform sinuses

• Channels in laryngopharynx
• End at the cricopharyngeal muscle

Valleculae

• Between base of tongue and epiglottis

Question 3

• What are the mechanisms of airway closure and which one is most important for airway protection?

Answer 3

• Ventricular fold closure either preceded or coincided with vocal fold closure
• Onset of vocal fold closure doesn’t seem to be fixed in relation to other laryngeal structure movement
• Vocal fold closure achieved by the time hyoid reached its maximum elevation
• Serves to reduce the chances of food/liquid entering the trachea and lungs

1. Larynx is closed off and moved up and forward
2. Cough is triggered if food/liquid enters larynx

Question 4

What is the major pressure generating forces that propels the bolus through the pharynx?

Answer 4

• Tongue base retraction!
• Constrictors generate pressure behind the bolus (CN X & XI)
• Tongue base forms a ramp, directing the bolus to the pharynx
• Tongue base retracts and pharynx bulges anteriorly at level of tongue base when bolus tail is at tongue base level
• The movement of these structures toward each other increases pharyngeal pressure
• Pressure increases as viscosity increases
• Pressure is applied to the tail of the bolus
• Once contact is made, pharyngeal walls continue to press the bolus downward

Question 5

What are the mechanisms for opening the esophagus?

Answer 5

Opening is caused by:

• Hyoid and laryngeal movement up and forward
• Relaxation of the muscle
• Bolus enlarges the opening as it is pushed into the esophagus